1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Lightweight buffered reading library. 4 * 5 * Copyright 2019 Google LLC. 6 */ 7 #ifndef __API_IO__ 8 #define __API_IO__ 9 10 #include <errno.h> 11 #include <poll.h> 12 #include <stdlib.h> 13 #include <string.h> 14 #include <unistd.h> 15 #include <linux/types.h> 16 17 struct io { 18 /* File descriptor being read/ */ 19 int fd; 20 /* Size of the read buffer. */ 21 unsigned int buf_len; 22 /* Pointer to storage for buffering read. */ 23 char *buf; 24 /* End of the storage. */ 25 char *end; 26 /* Currently accessed data pointer. */ 27 char *data; 28 /* Read timeout, 0 implies no timeout. */ 29 int timeout_ms; 30 /* Set true on when the end of file on read error. */ 31 bool eof; 32 }; 33 io__init(struct io * io,int fd,char * buf,unsigned int buf_len)34 static inline void io__init(struct io *io, int fd, 35 char *buf, unsigned int buf_len) 36 { 37 io->fd = fd; 38 io->buf_len = buf_len; 39 io->buf = buf; 40 io->end = buf; 41 io->data = buf; 42 io->timeout_ms = 0; 43 io->eof = false; 44 } 45 46 /* Reads one character from the "io" file with similar semantics to fgetc. */ io__get_char(struct io * io)47 static inline int io__get_char(struct io *io) 48 { 49 char *ptr = io->data; 50 51 if (io->eof) 52 return -1; 53 54 if (ptr == io->end) { 55 ssize_t n; 56 57 if (io->timeout_ms != 0) { 58 struct pollfd pfds[] = { 59 { 60 .fd = io->fd, 61 .events = POLLIN, 62 }, 63 }; 64 65 n = poll(pfds, 1, io->timeout_ms); 66 if (n == 0) 67 errno = ETIMEDOUT; 68 if (n > 0 && !(pfds[0].revents & POLLIN)) { 69 errno = EIO; 70 n = -1; 71 } 72 if (n <= 0) { 73 io->eof = true; 74 return -1; 75 } 76 } 77 n = read(io->fd, io->buf, io->buf_len); 78 79 if (n <= 0) { 80 io->eof = true; 81 return -1; 82 } 83 ptr = &io->buf[0]; 84 io->end = &io->buf[n]; 85 } 86 io->data = ptr + 1; 87 return *ptr; 88 } 89 90 /* Read a hexadecimal value with no 0x prefix into the out argument hex. If the 91 * first character isn't hexadecimal returns -2, io->eof returns -1, otherwise 92 * returns the character after the hexadecimal value which may be -1 for eof. 93 * If the read value is larger than a u64 the high-order bits will be dropped. 94 */ io__get_hex(struct io * io,__u64 * hex)95 static inline int io__get_hex(struct io *io, __u64 *hex) 96 { 97 bool first_read = true; 98 99 *hex = 0; 100 while (true) { 101 int ch = io__get_char(io); 102 103 if (ch < 0) 104 return ch; 105 if (ch >= '0' && ch <= '9') 106 *hex = (*hex << 4) | (ch - '0'); 107 else if (ch >= 'a' && ch <= 'f') 108 *hex = (*hex << 4) | (ch - 'a' + 10); 109 else if (ch >= 'A' && ch <= 'F') 110 *hex = (*hex << 4) | (ch - 'A' + 10); 111 else if (first_read) 112 return -2; 113 else 114 return ch; 115 first_read = false; 116 } 117 } 118 119 /* Read a positive decimal value with out argument dec. If the first character 120 * isn't a decimal returns -2, io->eof returns -1, otherwise returns the 121 * character after the decimal value which may be -1 for eof. If the read value 122 * is larger than a u64 the high-order bits will be dropped. 123 */ io__get_dec(struct io * io,__u64 * dec)124 static inline int io__get_dec(struct io *io, __u64 *dec) 125 { 126 bool first_read = true; 127 128 *dec = 0; 129 while (true) { 130 int ch = io__get_char(io); 131 132 if (ch < 0) 133 return ch; 134 if (ch >= '0' && ch <= '9') 135 *dec = (*dec * 10) + ch - '0'; 136 else if (first_read) 137 return -2; 138 else 139 return ch; 140 first_read = false; 141 } 142 } 143 144 /* Read up to and including the first newline following the pattern of getline. */ io__getline(struct io * io,char ** line_out,size_t * line_len_out)145 static inline ssize_t io__getline(struct io *io, char **line_out, size_t *line_len_out) 146 { 147 char buf[128]; 148 int buf_pos = 0; 149 char *line = NULL, *temp; 150 size_t line_len = 0; 151 int ch = 0; 152 153 /* TODO: reuse previously allocated memory. */ 154 free(*line_out); 155 while (ch != '\n') { 156 ch = io__get_char(io); 157 158 if (ch < 0) 159 break; 160 161 if (buf_pos == sizeof(buf)) { 162 temp = realloc(line, line_len + sizeof(buf)); 163 if (!temp) 164 goto err_out; 165 line = temp; 166 memcpy(&line[line_len], buf, sizeof(buf)); 167 line_len += sizeof(buf); 168 buf_pos = 0; 169 } 170 buf[buf_pos++] = (char)ch; 171 } 172 temp = realloc(line, line_len + buf_pos + 1); 173 if (!temp) 174 goto err_out; 175 line = temp; 176 memcpy(&line[line_len], buf, buf_pos); 177 line[line_len + buf_pos] = '\0'; 178 line_len += buf_pos; 179 *line_out = line; 180 *line_len_out = line_len; 181 return line_len; 182 err_out: 183 free(line); 184 return -ENOMEM; 185 } 186 187 #endif /* __API_IO__ */ 188